Rotating furnaces

ABSTRACT

A cooling system for cooling the ends of high-speed rotary furnaces which rotate about a generally horizontal axis. Two cylindrical shells are mounted coaxially on the external surface of one end of the furnace, at least the innermost of the two shells having a flange extending towards the axis of the furnace. Cooling water is directed under pressure from nozzles mounted on the furnace support structure between the innermost shell and the external surface of the furnace. These nozzles are inclined to a line parallel to the axis of the furnace so that the water is directed with a component of motion in the direction of rotation of the furnace. As the furnace rotates the water is forced by the pressure head built up as a result of the flange to pass between the innermost shell and the external surface of the furnace and then back between the two shells before being thrown outwardly into an annular collector surrounding the furnace.

United States Patent 1191 Barber 1 ROTATING FURNACES [75] Inventor: Brian Michael Barber, Middlesbrough, England [73] Assignee: The British Iron and Steel Research Association, London, England [22] Filed: Mar. 8, 1973 [21] Appl. No.: 339,310

[30] Foreign Application Priority Data l/l957 Great Britain... 34/242 Primary Examiner-John J. Camby Attorney, Agent, or I"irm- Bacon & Thomas; Jessie B. Grove,Jr.; Jerry A. Thieheau [5 7] ABSTRACT A cooling system for cooling the ends of high-speed rotary furnaces which rotate about a generally horizontal axis. Two cylindrical shells are mounted coaxially on the external surface of one end of the furnace, at least the innermost of the two shells having a flange extending towards the axis of the furnace. Cooling water is directed under pressure from nozzles mounted on the furnace support structure between the innermost shell and the external surface of the furnace. These nozzles are inclined to a line parallel to the axis of the furnace so that the water is directed with a component of motion in the direction of rotation of the furnace. As the furnace rotates the water is forced by the pressure head built up as a result of the flange to pass between the innermost shell and the external surface of the furnace and then back between the two shells before being thrown outwardly into an annular collector surrounding the furnace.

10 Claims, 3 Drawing Figures PATENTED APR 23 1974 SHEET 2 BF 2 1 ROTATING FURNACES rotating horizontally-disposed furnaces In these processes the furnace is rotated at a speed sufficiently high toensure that the liquid and solid contents of the furnace are maintained around the internal wall of the furnace by centrifugal force.

With all rotary furnaces which operate at a high temperature, the problem of cooling the external surface of the furnace arises. If the surface is not cooled, there is the possibility through overheating of damage to or distortion of the metal plates which normally surround the refractory lining of the furnace. It will be appreciated that any distortion of these metal plates could give rise to serious imbalance of the rotating furnace and lead to considerable mechanical damage. There is also the risk of break-outofmolten metal from the furnace'through damaged areas of the outer surface. In particular,

where the discharge end of the furnace is surrounded bya hood in which molten metal and slag are collected, the end ofthe furnace becomes extremely hot by virtue of the environment necessary for the successful collection of said molten metal and slag. This can result in l the burning away of the end of the shell which encloses the refractory lining of the furnace.

It is possible to provide general cooling of the furnace by water sprays situated around the. furnace. However, when the furnace is rotating at a high speed the water willbe thrown off the external surface of the furnace,

and this method is inadequate under high heat loads.

According to one aspect of the invention there is provided a metallurgical furnace installation having a rotatable furnace with an external surface and a stationary support structure, the installation including means for supplying and directing a cooling liquid under pressure along said external surface with a substantial component of motion in the direction of rotation of the fur nace.

According to a further aspect of the invention there is provided a method of treating material in a rotating :metallurgical; furnace having an external cylindrical surface, the step of supplying and directing a cooling liquid under pressure along said surface with a substantial component of motion in the direction of rotation of l the furnace. Preferably the installation also includes means for guiding the liquidalong said surface and pre-' venting the liquidfrom immediately being thrown off the surface under centrifugal force. Another optional feature is an annular collector mounted on the support structure surrounding the furnace to collect discharging liquid. i

The means for guiding the liquid may include first and second shells coaxial with and rigidly attached to the external surface of the furnace, the second shell being spaced outwardly from the first shell, the arrangement being such that liquid flows between said external surface and said first shell in one direction and then between said first and second shells in the opposite direction.

The installation preferably includes a flange at the liquid supply end of the first shell extending inwardly towards the axis of the furnace, said first flange providing in use a pressure head of liquid which forces the cooling liquid to circulate between the external surface of the furnace and the first shell .andsubsequ ently between the first and second shells. The second shell may.

have a flange at its liquid discharge end extending inwardly towards the axis of thefurnace. The flange of the first shell extends closer to the axis of the furnace than the flange of the second shell. In use, there will exist a pressure head of liquid between the inner end of the flange on the first shell and the inner end of the flange on the second shell.

The annular collector may have a U-shaped crosssection. Curved portions may extend from the xtremi ties of the limbs of the U and project towards one another partially to close the opening of the U. This prevents the majority of the liquid from splashing back from the upper portion of the collector onto the furnace shell. r

The means for supplying cooling liquid suitably includes a number of nozzles spaced around the furnace.

These nozzles may be fed by pipes from a ring main, and the full perimeter of the external surface can thereby be effectively cooled. The nozzles are preferably set at an angle to a line parallel to the axis of the furnace, so that the cooling liquid is directed with a substantial component of motion inthe direction of rotation of the furnace.

The diameter of the external surface of the furnace.

adjacent to one end of the furnace may be greater than the diameter of the external surface at the central portion of the furnace.

The furnace installation preferably includes a stationary furnace hood surrounding one end of the furnace and serving to collect molten material discharged from the furnace. The guiding means then extends into the region surrounded by the furnace hood.

In the accompanying drawings:

FIG. 1 shows a longitudinal section through one end i of one embodiment of a metallurgicalfurnace installation according to the invention,

FIG. 2 shows a detail of part of the furnace installation of FIG. 1, and

, FIG. 3 shows a crosssection on line IIIIII of FIG.

A rotatable furnace 2 consisting of a steel drum 4 of cylindrical form is mounted for rotation about its axis 5. The axis 5 is generally horizontally-disposed, being inclined at about 3 to the horizontal and not more than 8 to the horizontal. The drum 4 is supported by rollers (not shown) one or more of which rriay be driven by a motor to cause rotation of the furnace 2.

The drum 4 is lined with a layer of refractory material 6, and is open at both ends. Into the upper or inlet end, iron-making materials are fed, whilst liquid iron and slag is discharged from the lower or outlet end 7 into a refractory-lined hood 8 which is stationary and which surrounds the outlet end 7 of furnace 2. I

The hood 8 has a refractory-lined floor 9 which slopes downwardly to an opening 10 through which liquid metal and slag can bedischarged from the hood 8 into a ladle 11. An exhaust gas duct 12 extends horizontally from the hood 8 to a stack (not shown).

At the outlet end 7 of the furnace 2, the drum 4 is stepped outwardly, so that a cylindrical external surface 13 is provided at the outlet end 7 of the drum 4, the surface 13 having a diameter greater than the central portion of drum 4. As seen in enlarged view in FIGS. 2 and 3, first steel shell 14, coaxial with and spaced from surface 13, is rigidly attached to surface 13 by members 16 spaced around the circumference of surface 13. A second coaxial steel shell 15, spaced outwardly from the first shell 14, is rigidly attached to the extremity of surface 13 by an annular plate 17 which extends around the circumference of surface 13. There is a gap between the end of shell 14 and the annular plate 17. Both shells 14 and 15 have flanges, 18 and 19 respectively extending inwardly towards the axis of the furnace 2. Flange 18 at the water supply end of the first coaxial shell 14 extends closer to the axis 5 of furnace 2 than does flange 19 at the water discharge end of the second coaxial shell 15.

The portion of the refractory-lined hood 8 which surrounds the outlet end 7 of furnace 2 conforms to and is closely spaced from shells 14 and 15, so that the inner surface of hood 8 is not unduly cooled by cold air entering hood 8 through the resulting space. Attached to hood 8 where it surrounds the furnace 2 is an annular flanged section 30 which protrudes towards the furnace axis 5. The flanged section 30 interacts with a radial protrusion 31 from the second shell to form a seal between the furnace 2 and the hood 8.

An annular collector 20 surrounds the furnace 2 and end 7 of furnace 2. The collector 20 is not attached to the furnace 2, but is mounted on the furnace support structure which remains stationary. In cross-section, the collector 20 is U-shaped, having portions extending from' the extremities of the U and projecting towards one another partially to enclose the opening of the U.

Also attached to the furnace structure are water supply pipes 21 which are spaced around the furnace 2. Each pipe 21 has a nozzle 22 at one end and is connected with a water supply under pressure from a ring main at the other end. Each nozzle 22 is set at an angle of about 70 to a line parallel to the axis 5 of the furnace 2 so that the cooling water is directed with a substantial component of motion in the direction of rotation of the furnace 2. Both the nozzles 22 and the collector 20 are outside the region surrounded by furnace hood 8.

In the manufacture of iron, the rotating furnace 2 contains a layer of molten iron maintained against the refractory lining 6. A layer of molten slag and solid partly reduced materials, which is less dense than the iron, lies over the surface of the iron. Heat is supplied to the furnace 2 by combusting fuel supplied by a burner inserted in the inlet end of the furnace 2 and also combustion of the furnace gases, to provide energy for the reactions in the furnace contents. Molten iron and slag gradually flow along the furnace 2 to be discharged under centrifugal force from the outlet end 7 into hood 8. The molten iron and steel run down the walls of hood 8 and along the sloping floor 9 to run into the collection ladle 11. The waste gases produced by the combusted fuel pass through the hood 8 and into the exhaust gas duct 12, from where they are taken to a stack via suitable gas cleaning equipment.

Water is supplied continuously under pressure through pipes 21 and exits via nozzles 22 with a substantial component of motion in the direction of rotation of the furnace 2. The water also has a component of motion in a direction parallel to the axis 5 of furnace 2. The pressure of the water is adjusted depending on furnace rotational speed. As soon as the water comes into contact with the drum 4, the centrifugal forces tend to throw the water outwards away from the furnace 2. However the first shell 14 and its corresponding flange 18 prevent the water from moving away from the drum 4 and result in the build up of a pressure head of water due to the centrifugal force involved. Water is thereby forced under pressure into the space between the external surface 13 of the furnace 2 and the first shell 14 and guided along surface 13. The water is prevented from immediately being thrown off the surface 13 under centrifugal force by first shell 14. Water then flows through the gap between the end of first shell 14 and the annular plate 17, finally flowing between first shell 14 and second shell 15 in a direction opposite to the direction of flow between surface 13 and first shell 14.

The flange 19 attached to the second shell 15 permits the water to be discharged more or less radially from the furnace 2. Flange 19 also provides a means for controlling the pressure head of water, so that the required flow of water for cooling purposes passes along the external surfaces 13, 17 and 15 of furnace 2.

Water discharged from the furnace 2 is thrown outwards in the U-shaped collector 20, where the portions extending from the extremities of the U and projecting towards one another prevent the water from splashing back from the upper part of the collector 20. The water then runs down the collector 20 and is run of at its lower end.

The cooling water, not warm, may be cooled by conventional means and recycled into the furnace cooling system if so desired. The central portion of the furnace outer surface may be cooled by a forced flow of cool air or by additional water sprays situated around the furnace.

The outer surface of the end portion of the furnace, although illustrated as being perfectly cylindrical, may be inclined towards or awayfrom the axis of the furnace.

The spacing of the coaxial shells will depend upon the temperature of operation of the furnace, the diameter of the furnace, and the materials from which the refractory lining of the furnace and the outer surface of the furnace are made. These factors will dictate the cooling water flow rates required to ensure adequate cooling of the end of the furnace.

The invention thus provides in particular an extremely satisfactory means of cooling the ends of rotating furnaces which extend into hot environments.

We claim:

l. A metallurgical furnace installation including a high speed rotatable furnace having an internal refractory lining and an externally generally cylindrical surface, a stationary structure for supporting said furnace for rotation about a generally horizontally axis; pipes and nozzles mounted on said structure for supplying and directing a cooling liquid under pressure along said external surface of the furnace, said nozzles being set at an acute angle to a line parallel to the axis of the furnace so that the cooling liquid is directed with a substantial component of motion in the direction of rotation of the furnace, said installation including first and second shells co-axial with the furnace, both shells being rigidly attached to the external surface of the furnace, and said second shell being spaced outwardly from said first shell and mounted at one of its ends to an annular plate extending from the external surface of the furnace, the arrangement being such that cooling liquid may flow between said external surface and said first shell in one direction and is then deflected by the annular plate so that it flows between said first shell and said second shell in an opposed direction.

2. An installation according to claim 1 including a flange at the liquid supply end of said first shell extending inwardly toward the axis of the furnace, said flange providing in use a pressure head of liquid under centrifugal force which causes the cooling liquid to flow between the external surface of the furnace and the first shell and subsequently between the first and second shells.

3. An installation according to claim 2 in which the second shell has a flange at its liquid discharge end extending inwardly towards the axis of the furnace, the flange of said first shell extending closer to the axis of the furnace than the flange of the second shell.

4. An installation according to claim 1 including an annular collector mounted on the supportstructure surrounding the furnace to collect discharged liquid.

5. An installation according to claim 4 in which the annular collector is of U-shaped cross section and curved portion extending from the extremities of the limbs of the U projecttoward one another partially to close the opening of the U.

6. An installation according to claim 1 in which the diameter of the external surface of the furnace adjacent one end of the furnace is greater than the diameter of the external surface of a central portion of the furnace.

7. An installation according to claim 1 including a stationary furnace hood surrounding one end of the furnace and serving to collect molten material discharged from the furnace.

8. An installation according to claim 1 in which the liquid supplying and directing means includes supply pipes and nozzles on the ends of said supply pipes.

9. In a method of treating material in a horizontally disposed high speed rotating metallurgical furnace having a generally cylindrical external surface, and first and second shells co-axial with the furnace, both shells being rigidly attached to the external surface of the furnace, said second shell being spaced outwardly from said first shell and mounted at one of its ends to an annular plate extending from the external surface of the furnace, the step of supplying and directing a cooling liquid under pressure along said external surface with a substantial component of motionin the direction of rotation of the furnace, the cooling liquid then flowing between said external surface and. said first shell in one direction and being deflected by the annular plate so that it flows between said first shell and said second shell in an opposed direction.

10. A method according to claim 9 including continuously forming the cooling liquid having the component of motion into an annular body ofliquid, and causing liquid from the annular body to flow between the external surface of the furnace and the first shell and.

between the first and second shells by centrifugal force. 

1. A metallurgical furnace installation including a high speed rotatable furnace having an internal refractory lining and an externally generally cylindrical surface, a stationary structure for supporting said furnace for rotation about a generally horizontally axis; pipes and nozzles mounted on said structure for supplying and directing a cooling liquid under pressure along said external surface of the furnace, said nozzles being set at an acute angle to a line parallel to the axis of the furnace so that the cooling liquid is directed with a substantial component of motion in the direction of rotation of the furnace, said installation including first and second shells co-axial with the furnace, both shells being rigidly attached to the external surface of the furnace, and said second shell being spaced outwardly from said first shell and mounted at one of its ends to an annular plate extending from the external surface of the furnace, the arrangement being such that cooling liquid may flow between said external surface and said first shell in one direction and is then deflected by the annular plate so that it flows between said first shell and said second shell in an opposed direction.
 2. An installation according to claim 1 including a flange at the liquid supply end of said first shell extending inwardly toward the axis of the furnace, said flange providing in use a pressure head of liquid under centrifugal force which causes the cooling liquid to flow between the external surface of the furnace and the first shell and subsequently between the first and second shells.
 3. An installation According to claim 2 in which the second shell has a flange at its liquid discharge end extending inwardly towards the axis of the furnace, the flange of said first shell extending closer to the axis of the furnace than the flange of the second shell.
 4. An installation according to claim 1 including an annular collector mounted on the support structure surrounding the furnace to collect discharged liquid.
 5. An installation according to claim 4 in which the annular collector is of U-shaped cross section and curved portion extending from the extremities of the limbs of the U project toward one another partially to close the opening of the U.
 6. An installation according to claim 1 in which the diameter of the external surface of the furnace adjacent one end of the furnace is greater than the diameter of the external surface of a central portion of the furnace.
 7. An installation according to claim 1 including a stationary furnace hood surrounding one end of the furnace and serving to collect molten material discharged from the furnace.
 8. An installation according to claim 1 in which the liquid supplying and directing means includes supply pipes and nozzles on the ends of said supply pipes.
 9. In a method of treating material in a horizontally disposed high speed rotating metallurgical furnace having a generally cylindrical external surface, and first and second shells co-axial with the furnace, both shells being rigidly attached to the external surface of the furnace, said second shell being spaced outwardly from said first shell and mounted at one of its ends to an annular plate extending from the external surface of the furnace, the step of supplying and directing a cooling liquid under pressure along said external surface with a substantial component of motion in the direction of rotation of the furnace, the cooling liquid then flowing between said external surface and said first shell in one direction and being deflected by the annular plate so that it flows between said first shell and said second shell in an opposed direction.
 10. A method according to claim 9 including continuously forming the cooling liquid having the component of motion into an annular body of liquid, and causing liquid from the annular body to flow between the external surface of the furnace and the first shell and between the first and second shells by centrifugal force. 